The invention is related to pivoting workpiece supports and adjustment mechanisms for use therewith.
Pivoting workpiece supports are utilized in a number of manufacturing environments to provide a variable orientable work surface for the assembly of components such as printed circuit assemblies, computer hard drives, automotive components, etc.
With a pivoting workpiece support, a platform is pivotably supported on a base, with a rotational coupling utilized to secure the platform support to the base. An adjustment mechanism may also be coupled to the workpiece support to permit an operator to adjust the relative angle of the platform.
One benefit of a pivoting workpiece support is the fact that the platform can be adjusted for use with different operators, or may be adjusted by a single operator to optimize the orientation of the platform for different tasks. In addition, a pivoting platform may also be used to permit multiple sides of a workpiece to be accessed at a comfortable orientation for an operator.
To maximize an operator""s productivity when using a workpiece support, it is desirable for the adjustment mechanism to be as fast and easy to operate as possible. Also, given that an operator can exert significant torque while working on a platform, it is also desirable for an adjustment mechanism to be secure and reliable to minimize unwanted movements of the platform.
Conventional adjustment mechanisms such as set screws have been used to selectively lock a platform in a desired rotational orientation for extended periods of time. With a set screw, a threaded screw is oriented perpendicular to a pivot shaft for radial movement relative to the axis of rotation of the pivot shaft. Rotation of the threaded screw applies a force through the end of the screw to the pivot shaft to restrict rotation of the pivot shaft about its axis of rotation.
One problem with set screws and the like is that they are often difficult to manipulate in a fast and efficient manner. Some set screws may require several turns both to release and re-secure the pivot shaft. In addition, the force required to twist a set screw may induce fatigue in an operator, particularly if the operator makes frequent adjustments. As a consequence, set screws are not typically used in environments where repetitive adjustments are required.
One conventional adjustment mechanism utilized in some pivoting workpiece supports is a pawl and ratchet design, where a toothed wheel coupled to a pivot shaft is engaged by a pawl to selectively permit or restrict rotation of the pivot shaft. Other mechanisms utilize a spring-loaded shot pin configured to engage in one of a plurality of holes disposed circumferentially around a shaft. Conventional pawl and ratchet designs and shot pin designs, however, are not infinitely adjustable, and are restricted by the number of teeth disposed on the ratchet or holes disposed on a shaft. Such designs may also be slow and cumbersome, and may require significant effort to operate.
Therefore, a significant need continues to exist in the art for a fast and efficient adjustment mechanism for use with pivoting workpiece supports and the like.
The invention addresses these and other problems associated with the prior art by providing a clutch and a workpiece support incorporating the same in which rotation of a rotatable member is selectively restricted through the use of one or more rollers that are pinched between the outer surface of the rotatable member and corresponding convergent surfaces disposed on a housing opposing such outer surface. In effect, each roller is interposed between a surface on a fixed housing and an outer surface of a rotatable member such that rotation of the rotatable member rolls the roller toward a converging gap to restrict further rotation of the rotatable member. A biasing mechanism biases the roller toward the converging gap, and a release mechanism is utilized to quickly and efficiently decouple the roller from the rotatable member by biasing the roller in a direction away from the converging gap and thereby preventing the roller from inhibiting rotation of the rotatable member.
Consistent with one aspect of the invention, therefore, a clutch is provided for use in selectively restricting rotation of a rotatable member that rotates within a rotational plane and about an axis of rotation. The rotatable member includes an annular engagement surface circumscribing the axis of rotation. Moreover, the clutch comprises a housing having defined thereon a convergent surface opposing the annular surface of the rotatable member and separated therefrom by a gap that decreases between first and second positions within the rotational plane of the rotatable member. The clutch also includes a roller disposed within the gap between the convergent and annular surfaces, the roller configured to rotate about an axis of rotation that is parallel to the axis of rotation of the rotatable member, and the roller having a diameter that is less than the gap between the convergent and annular surfaces proximate the first position, but is greater than or equal to the gap between the convergent and annular surfaces proximate the second position. The clutch further includes a biasing mechanism coupled to the roller and configured to bias the roller toward the second position to wedge the roller between the convergent and annular surfaces and thereby restrict rotation of the rotatable member, and a release mechanism coupled to the roller and configured to selectively oppose the biasing mechanism to bias the roller toward the first position and permit rotation of the rotatable member.
Consistent with another aspect of the invention, a workpiece support is provided comprising a base and a platform, with the platform pivotably coupled to the base through an adjustment mechanism incorporating a clutch having the features described above to selectively permit pivoting of the platform relative to the base.
These and other advantages and features, which characterize the invention, are set forth in the claims annexed hereto and forming a further part hereof. However, for a better understanding of the invention, and of the advantages and objectives attained through its use, reference should be made to the Drawings, and to the accompanying descriptive matter, in which there is described exemplary embodiments of the invention.